Shocer (oz12679)

 

Shocer (oz12679) by Mel Schmidt 1972 - plan thumbnail

About this Plan

Shocer. Free flight power competition model.

Quote: "AMA's District X F/F Contest Board Member and MODEL BUILDER's columnist for 'The Unattached' presents the main ingredient for beating the competition in 1972. Shocer, by Mel Schmidt.

The Shocer is well suited for the new 1972 free flight rules and is intended for use in a tough competitive field. It is thoroughly proven and has been developed to win. For power safety, a long fuselage with a relatively large rear fin and stabilizer are used. Built-in warps and incidence, along with high power, corkscrew the Shocer up to a floating glide. For consistency, surfaces are designed to be rigid and free from warp changes.

In this article, emphasis is placed on flight trimming and design reasoning. Flight trimming is the source of most problems yet many design articles hardly touch on the subject. We hope that this design and text contribute in some way to your understanding of contest free flight. Flying a modern contest free flight is something like mountain climbing. It is an emotional experience. Succeed and you have a machine of truly amazing performance; a machine which accelerates from your hand to a breath-taking climb and floating glide. Fail, and in just a few seconds, you may have nothing. It requires courage to release that first flight, and fortitude, grit and backbone to rebuild after making a mistake. Just remember that the machine only does what it is told to do. It doesn't think, nor is it mystic.

Power, stability, and control were obtained by the following:

(1) From ships designed and flown, it has been found that the control of power is improved as the CG is moved back. On this design the CG is at 85% of the wing cord.

(2) Using a larger size stab makes the exact location of the center of gravity less critical and generally makes the plane more forgiving and stable under power. The control of power has been improved as the stab was increased from 29% to 37% of the wing area.

(3) An unrestricted propeller slip-stream which passes directly over the tail and under the wing has proven to be a big item in controlling power. The movement caused by the up load at the tail, a long distance from the CG, is more powerful in preventing loops. Test flights have proven that under high power this design has little tendency to loop or turn. This confirms the stabilizing effect of the rear of the ship.

(4) An ultra short nose seems to reduce the effects that torque changes have on flight trim. The control of power improved as the nose length was shortened.

(5) From many flights it has been learned that small tails and short fuselages cause real power handling problems. Up to a point, the control of power is improved as the tail is increased in size and the fuselage is lengthened.

(6) High aspect ratio wings (over 8-1/2) are generally troublesome under very high power. A moderate aspect ratio of around 7 1/2 seems a good compromise and the glide will not suffer if the wing loading is kept reasonably low.

(7) On this design, with a rather large vertical tail and high pylon, the slipstream has a lot to act on. The slipstream twist acting on the pylon tends to cause a right turn, the high vertical tail causes a left turn, and the low vertical tail causes a right turn. The result is a natural right turn under high power. Heavy wash-in on the right wing is used to cause a vertical spiral. Flying without the heavy wash-in would result in a right dive while flying with wash-in and improper pylon/tail areas or misaligned structures could easily result in a left spiral from high altitudes.

(8) The ship's size may be of some interest. The ideal is simply this: The model should climb as high as possible and should weigh no more than necessary, all with reliability, consistency and performance. The photos show the fourth ship built by the author. Seven others have been built and flown by Don Zink and Paul Ryan of Southern California, and Bob Watson of Chicago.

(9) The use of left. thrust, right rudder tab, and sufficient climb speed guarantee a good transition. A good transition can also be obtained by using an auto rudder and no left thrust. Mount a Tatone Flood-off inverted and use the fuel trip to double as an auto rudder release. The fuel flood-off and auto rudder trip at the same instant..."

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Shocer (oz12679) by Mel Schmidt 1972 - model pic

Datafile:
  • (oz12679)
    Shocer
    by Mel Schmidt
    from Model Builder
    January 1972 
    66in span
    IC F/F
    clean :)
    all formers complete :)
    got article :)
  • Submitted: 25/11/2020
    Filesize: 609KB
    Format: • PDFbitmap
    Credit*: MB2020
    Downloads: 353

Shocer (oz12679) by Mel Schmidt 1972 - pic 003.jpg
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Shocer (oz12679) by Mel Schmidt 1972 - pic 004.jpg
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